This invention relates to apparatus for reheating the exhaust steam or other working fluid from an external combustion engine, e.g., a turbine.
One of the most important uses of the apparatus is that of a steam regenerator in power stations where it receives exhaust steam from the turbine and takes over some or all of the functions of the stationary boiler.
In a nuclear power station the apparatus may be used as a steam superheater thus increasing the thermal efficiency.
The conventional condensers are eliminated by the present invention. A vacuum (0.04 atm.) in the condenser of a conventional steam plant allows a further expansion in the exhaust stage of the turbine which contributes to increasing the latter's efficiency. Since the condenser, however, requires a lot of water (60-100 times as much as steam) the construction of a power station mainly depends on the water supply.
The solution of this problem has become more and more difficult especially with respect to nuclear power stations as the events of recent days have taught us.
The condensing-turbine works nowadays with a degree of efficiency of its own of 70-72%, whereas its total degree of efficiency, however, may decrease to 35-40% according to the technological design governing the utility of heat. In other words, the total efficiency of a power station operating with steam turbines depends on the thermal fall or, in our case, of the steam enthalpy being 400-500 Kcal/Kg for condensing-turbines with great efficiency and 150-250 Kcal/Kg for counter-pressure turbines, whereas the total enthalpy of fresh steam amounts to 700-860 Kcal/Kg (for 600.degree. C. and 200 atm.). So we can observe an enormous loss of heat in such stations and as a consequence, only 30% of the fuel energy which is supplied is transformed into mechanical work.
For years the phenomenon of condensation has supported the conviction that heat from steam evaporation can be obtained by means of the condenser. Nevertheless, it is a well known fact that 60% of the total steam heat is taken away by the cooling medium, plus 5% other heat losses.
A temperature fall takes place in the condenser, but the vacuum is the only effect of condensation and it is paralleled by the decrease in enthalpy and is advantageous. Some authors give the following results: 1% vacuum (more than 90%) corresponds to 1% of fresh steam. But they all agree upon the statement that for thermodynamic reasons the condenser requires an enormous supply of energy. According to the Mollier h-s diagram the decrease in enthalpy can maximally amount to 210 Kcal/Kg for steam under a pressure of 1 atm. (97% vacuum). Consequently 329.4 Kcal/Kg are lost. The same applies to the counter-pressure turbine in which after having passed the turbine the steam is reutilized and transformed into water by condensation--a natural phenomenon--but this transformation results in the evaporation heat being lost (at a minimum 539.4 Kcal/Kg with 1 atm. and 100.degree. C.). In order to avoid such an important loss of heat, the enthalpy of the steam must be increased again after having passed the last stage of the turbine to avoid being a quantity of steam transformed into water. Consequently, the condenser must be substituted by a new device.
The apparatus of the present invention can be used as a steam supply for an energy producing plant irrespective of whether it is stationary or mobile (locomotives, vessels or other vehicles). In chemical plants there are processes which require very high pressures and temperatures, and in this field of application the compressors and fans presently used can be successfully replaced by a regenerator in accordance with the present invention. In metallurgy the present invention can be used as a hot-air compressor, as for example, for a blast furnace; or it can replace axial compressors in power stations operating with gas turbines.